internal-slot

internal-slot

Truly private storage, akin to the JS spec’s concept of internal slots.

Uses a WeakMap when available; a Map when not; and a regular object in even older engines. Performance and garbage collection behavior will reflect the environment’s capabilities accordingly.

Example

var SLOT = require('internal-slot');
var assert = require('assert');

var o = {};

assert.throws(function () { SLOT.assert(o, 'foo'); });

assert.equal(SLOT.has(o, 'foo'), false);
assert.equal(SLOT.get(o, 'foo'), undefined);

SLOT.set(o, 'foo', 42);

assert.equal(SLOT.has(o, 'foo'), true);
assert.equal(SLOT.get(o, 'foo'), 42);

assert.doesNotThrow(function () { SLOT.assert(o, 'foo'); });

Tests

Simply clone the repo, npm install, and run npm test

Security

Please email @ljharb or see https://tidelift.com/security if you have a potential security vulnerability to report.

Changelog

v1.1.0

13 December 2024

• [New] add types 295d25d
• [actions] split out node 10-20, and 20+ 9c9a2ab
• [Dev Deps] update @ljharb/eslint-config, auto-changelog, object-inspect, tape 9c5621b
• [Deps] update hasown, side-channel 5281391
• [Tests] replace aud with npm audit 64ce191
• [Dev Deps] add missing peer dep d500343